The present invention generally relates to uses of recombinant expression vectors expressing foreign proteins in controlling insects, and more particularly to a method utilizing insect pathogens, preferably recombinant, in conjunction with synthetic chemical insecticides to magnify insect kill rate.
The lepidopteran family Noctuidae includes some of the most destructive agricultural pests, such as the genera Heliothis, Heliocoverpa, Spodoptera, and Trichoplusia. For example, included in this family are the tobacco budworm (Heliothis virescens), the cotton bollworm (Heliocoverpa zea), the cotton leafworm (Alabama argillacea), the spotted cutworm (Amathes c-nigrum), the glassy cutworm (Crymodes devastator), the bronzed cutworm (Nephelodes emmedonia), the fall armyworm (Laphygma frugiperda), the beet armyworm (Spodoptera exigua), and the variegated cutworm (Peridroma saucia). Attempts to control these and other insects have often involved the use of pyrethroid insecticides. Wildtype baculoviruses have been used with limited commercial success.
Pyrethroid insecticides now dominate the insecticide market with sales reaching into the billions annually. However, sales are beginning to stalemate due in part to the wide-scale presence of pest resistance to these compounds. In cotton alone, the presence of pyr-R Heliothis species has begun to result in millions of lost dollars annually. In fact, in several cases pyrethroid insecticides have completely failed to control infestations of Heliothis larvae in cotton, which has resulted in complete destruction of the crop. Consequently, there has been an enormous effort to control pyrethroid resistance in Heliothis species in cotton.
Agricultural producers sometimes attempt to restrain their use of pyrethroid insecticides until late in the growing season as a strategy against pyrethroid resistance. As a result, the producers have to turn to the less effective and more expensive organophosphate and carbamate insecticides, which have also been plagued with resistance problems. Therefore, the development of a new and effective pesticide to control pyr-R pests would be extremely valuable in any management strategy.
Resistance of agricultural pests to pesticides also leads to environmental and human health risks. These problems arise because another response by producers to pyrethroid (and other insecticide) resistance is the use of increasing amounts of pesticide, and the use of more non-selective and toxic compounds, in order to overcome pest resistance. This creates a destructive and vicious cycle.
Nevertheless, the uses of synthetic chemicals, such as exemplified by the pyrethroids, are an integral component of modern agriculture and are probably necessary to maintain our current level of agriculture productivity, although alternative control agents, such as the earlier mentioned recombinant insect pathogens, are being explored for pest control.
Recently, the nuclear polyhedrosis virus Autographa californica (AcNPV), from the family Baculoviridae, has been genetically modified for an increased speed of kill by expressing insect-selective toxins. The introduction of insect-selective toxins into an insect-pathogenic virus has resulted in an approximate 30% reduction in the killing time of insect hosts, as is described by U.S. Ser. No. 08/472,053, filed Jun. 6, 1995 which is a continuation-in-part of U.S. Ser. No. 08/229,417, filed Apr. 15, 1994, abandoned, which is a continuation-in-part application of U.S. Ser. No. 07/629,603, filed Dec. 19, 1990, abandoned, having (in part) common assignment herewith.
Among the insect specific toxins suggested for use in insect control are toxins from Bacillus thuringiensis from the scorpions Buthus eupeus and Androctonus australis and from the mite Pyemotes tritici. Further, Hammock et al., (Nature, 344, pp. 458-461, 1990) have described use of JHE to control insects, U.S. Ser. No. 08/440,520, filed May 12, 1995, U.S. Pat. No. 5,674,747 U.S. Ser. No. 07/927,851, filed Aug. 10, 1992, U.S. Pat. No. 5,643,776 and U.S. Pat. No. 5,098,706, issued Mar. 24, 1992, all of common assignment herewith.
A new tool to control resistant, as well as susceptible, insect pest populations would be very desirable.
In one aspect of the present invention, a method for controlling pests is provided. Pests controlled in accordance with the invention are, for example, from the group insects, acarids, and nematodes. Such pests are treated (or their loci treated) with a synergistic combination of recombinant virus and organic insecticide. The recombinant virus preferably is a baculovirus that expresses a foreign protein or a functional derivative thereof in pest cells infected with the recombinant baculovirus.
Treatments in accordance with the invention can be simultaneous (such as by applying a pre-mixed composition of recombinant virus and organic insecticide). Alternatively, the pests or loci may first be treated by applying virus followed by organic insecticide within about 24 hours.